In most cases I've seen the workflow andor the session did not even run, so of course you cannot retrieve any "up-to-date" log file (because it simply doesn't exist).
For example, if the value of a session parameter for a relational connection (a session parameter named "$DbConnection" followed by whatever name, e.g. "$DbConnectionEdwStage") cannot be resolved using the parameter file, the workflow won't even start; trying to get a workflow log for this workflow run will result in the error message you've seen.
You can find these errors either in the lower windows of the Workflow Monitor or in the log files of the Integration Service.
Verified the IS log & identified the issue.
Issue has been resolved.